Alternating current-direct current pulsing circuits for register senders



April 28, 1953 G. DEAKIN 2,635,946

ALTERNATING CURRENT-DIRECT CURRENT PULSING CIRCUITS FOR REGISTER SENDERS Filed June 22, 1948 5 Sheets-Sheet 1 INVENTOR. GER/4L0 DEA/(IN Wwk AZTQKNEY V April 28, 1953 G. DEAKIN 2,636,946

ALTERNATING CURRENT-DIRECT CURRENT PULSING CIRCUITS FOR REGISTER SENDERS Filed June 22, 1948 3 Sheets-Sheet 2 rAM-IHI INVENTOR.

65 F191. 0 DEH/f/N Apnl 28, 1953 G. DEAKIN 2,636,946

ALTERNATING CURRENT-DIRECT CURRENT PULSING CIRCUITS FOR REGISTER SENDERS Filed June 22, 1948 5 Sheets-Sheet S IN VEN TOR. GERALD 0154K l/V ATTORNEY Patented Apr. 28, 1953 ALTERNATING CURRENT-DIRECT CURRENT PULSING CIRCUITS FOR B E G I S T E.

SENDERS Gerald Deakin, New York,N. Y., assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application J uue 22, 948, Se ial N 0. 3 ,525

3 Claims.

This invention relates to new and useful improvements in automatic switching systems, such vas are used in telephone exchanges, and more particularly in the pulsing circuits of such sysems.

The object of the invention is to provide, .in a register attached to a calling line in the manner shown in my prior patents, a simple and efficient means for counting and storing the impulses representing the digits of a number, the pulses being produced by one or the other of two types of pulse senders or controllers.

In the one case the pulse sender is the conventional calling dial which opens the line circuit to produce a pulse. This dial is adapted to produce one to ten pulses depending upon the movement of the finger wheel.

In the other case the pulse sender, instead of opening the line to produce a pulse, closes theline through a rectifier, thus limiting the flow of current in the line circuit to current of one polarity and then alternately reverses the polarity. This action provides for the operation and release of polarized relays located in the register and connect-edto a source of alternating current. The

pulse sender or controller is adapted to produce a maximum of live pulses of alternate polarities. The ten digits are represented by two groups of pulses, the groups being distinguished one from jthe other by the polarity and duration of the starting or first pulse of the series. A rectifier 'sender of the above type has been disclosed in my Patent No. 2,433,347.

A feature of the invention is the ability of the register to recognize the polarity of the first or starting pulse and to adjust the pulse counting relays to register properly the pulses that follow.

The register is also provided with means for arranging its pulse receiving circuit to operate in connection with the type of controller or sendor to be used for recording. The same groups of .pulse counting relays are used for counting and recording the pulses produced by either type .of ,sender.

The tTOOVCuH'lEIlti-Ollfld and other features and objects of this invention and the manner of at taining them will become more apparentand the invention will be best understood, by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a diagram which illustrates the theory I interrupter.

. Figs. 2,3 and 4 are diagrams which illustrate o an) the theory of rectifier pulsing with alternating curr n Fig. 5 is a diagram showing the subscribers line With the open circuit dial sender.

Fig. 6, which should be placed below Fig. 5, is a diagram of the pulse receiving circuit.

Fig. 7, which should be placed. below Fig. 6, is a diagram of the pulse counting and storing cirouit.

Fig. 8 is a diagram corresponding to s- 5 but showing a rectifier send r with h parts in he position to pass current of one polarity.

Fig. 9 is a diagram of the same rectifier sender with the parts in the position to pass current of the opposite polarity.

The circuits of Figs. .5 t .9 inclusive show only those circuit elements necessary for a complete understanding of the inven ion. The subscribers st tion indicated in .Fi 5 has a sender of the open circuit pulsing ype with thedial and ringer di mmatical y epres nt d. I will be understood that a plurality of su scriber station a connected to th register shown Fi s- 6 and 7 by the conventional links indic ted by t e 'boX l0 and shown more fully in my prior patents, Figs. 8 and .9 represent diagrammatically a recti ier sender in the two poss ble positions of he rectiher. A plurality of these subsc ibe s st ons may also be connected to the link circuit H) for selec ive conn ction t the system- The pul e receivin circuit of Fi 6 and the pulse count- 'ing and storing circuit of Fig. 7. ar parts of a register circuit which provides for nlulti1ootential selection. For a more complete register circuit of this type reference may be made to my prior pa nts such as Patent 2,380,950, issued Au ust 7. 1.9.4.5.

GENERAL THEORY The register circuit is adapted for Open circuit puls ng nd rectifier pu sing. By open ircuit pulsing is m ant the opening and closin of the line circuit for each puls as with the d al now in use. By rectifier pulsing is meant the connection of a rectifier in th line circuit so as to permit the positive and negative components of the altern ing current to pass alternately throu h the circuit. The source of alternating current may vary in freque cy such as from 133 cycles to 400 cycles. The main exchange storage -batte y is u ed ior op n circuit dialling- -In the i l-re ister ircu t direct current is norinally onnectedso that when a line is equipped ,for open circui pulsing calls, no change is required. However, when a line is equipped for 3 rectifier pulsing calls, the register circuit is arranged to automatically disconnect the source of direct current potential and connect the alternating current source at the start of the first pulse.

Definitions for positive and negative pulses in alternating current pulsing In order to avoid confusion in understanding the following description, it is well to have defi- 'nitely in mind what is meant by a negative pulse and what is meant by a positive pulse. The definitions used herein are arbitrary, but as the negative pole of the exchange battery is usually associated with the b wire, a current pulse which flows from the a wire to the b wire through the subscribers set is herein considered a negative pulse. Consequently, a current pulse which flows from the 1) wire to the a wire through the subscribers set is considered a positive pulse. Furthermore, the pulse counting circuit may be operated over the front contact of the pulsing relay or over the back contact. When it is operated over the front contact, the count is made at the beginning of a pulse; when it is operated over the back contact, the count is made at the end of a pulse.

Open circuit pulsing with direct current When the line circuit is opened, as indicated in Fig. 1, both pulsing relays PR! and PR2 fall off and make their back contacts.

Rectifier pulsing with alternating current The theory of alternating current pulsing may be best understood by reference to Figs. 2, 3 and 4. The pulsing circuit comprises a source of alternating current, indicated at A. 0., two low impedances, relatively high resistance, pulsing relays, PR] and PR2, two rectifiers, SI and S2, two capacitors, Cl and C2, and one resistor RI.

When the handset is removed and the line circuit closed, the circuit becomes as shown in Fig. 2. The positive pulsations operate relay PR2 and the current flows from one pole of the alternating current source through rectifier S2, winding PR2, in multiple with capacitor C2, line from the b to the a wire resistor Rl to the other pole of the alternating current source. The negative pulsations operate relay PRI in a similar manner when current fiows in the opposite direction. During the current reversals the relays remain on their front contacts because of the charged and bridged capacitors which tend to sustain the current after the pulsation ceases. For example, in the case of relay PRI, this term porary sustaining current fiows from capacitor CI. The relays are very sensitive and will follow the alternating current frequency when capacitors are not connected.

When a rectifier sender is used, the alternating current during a given pulse becomes a pulsating current flowing in one direction only; that is, in the direction permitted by the polarization of the rectifier S3 at the subscribers station. Rectifier S3 is shown polarized for a terminating negative pulse in Fig. 3. Relay PR! is maintained on its front contact but relay PR2 releases and makes its back contact and counts the pulse.

When the polarization of the rectifier S3 is reversed, as shown in Fig. 4, for a terminating positive pulse, relay PRI makes its back contact and counts the pulse while relay PR2 maintains its front contact.

For a given relay speed, rectifier pulsing, in theory, is four times as fast as open circuit pulsing for two reasons:

a. With open circuit pulsing a maximum of ten pulses is required and only one count is made per time interval and that is when the single pulsing relay makes it back contact. When the relay is on its front contact, the time is lost, so far as pulses are concerned.

22. With rectifier pulsing a maximum of only five pulses is required and two pulses are produced per time interval, one by each of two pulsing relays. During one half of the time interval one relay makes its back contact and makes one count; during the other half of the time interval the other relay makes its back contact and makes a second count. Thus two pulses are recorded in one time interval.

By cutting the time in half and by cutting the number of pulses in half, the theoretical speed is increased fourfold.

In actual practice, full advantage cannot be taken of this theoretical fourfold increase in speed because the changeover time from one digit to the next is approximately one-half instead of one-fourth. Taking all things into consideration, rectifier dialling in actual practice increases the speed of sending two to three times, depending upon the digit.

SUBSCRIBERS STATION DIAL OR SENDER Open circuit dial The open circuit dial is the ordinary dial now in general use.

Rectifier sender A rectifier sender may be of many designs making use of the principles disclosed in my above-mentioned Patent No. 2,433,347. It should be capable of generating two series of five pulses alternately positive and negative, one series to start with a short positive pulse following negative current flow produced as the sender is set and the other with a long positive pulse which is a combination of positive current flow produced as the sender is set and the first positive pulse.

In order to accomplish this, the rectifier sender is provided with a direct current bridge or short circuiting connection which remains bridging the rectifier during most of the time the lever is moving towards the finger stop. In the case of digit from 1 to 5, for instance, the direct current bridge is connected until the finger stop is reached, whereupon the rectifier is in position to permit a negative pulse. In the case of digits from 6 to 0, the direct current bridge is connected until the lever has moved part way through the first, or number 6, position, whereupon the rectifier is connected so as to permit a positive pulse and it remains so connected in the finger stop position. I

The order, polarity and number of pulses for which the register circuit of Figs. 6 and '7 is designed are shown in Tables I and II. In these tables the potentials corresponding to the successive positions through which the lever moves in sending a particular digit are listed in the vertical columns, there being two of these columns for each digit. The column marked A" shows the potentials from top to bottom as the lever is moved to arrive at the finger stop; that marked R shows the succession of potentials from bottom to top as the lever leaves the finger stop. It will be understood that the first movement of the lever tells the register which group of five digits the particular digit is in and the return movement sends the counting pulses. lhe connection of the direct current bridge is indicated by D. C'.

TABLE I potential PC operates relay CR2 which adjusts the register for operation with the rectifier sender.

The register is provided with pulse receiving relays shown in Fig. 6 which respond to the Polarity of S3 for digits 1 to 1 2 3 4' 5 Digit; position A R A R A R A R A R n. o n-. o. F/3Y6" 4 1 3' 8 3 D.' o DI o1 DI o 1 +lD. C. D. C. D. C. D... 0 Finger Stop TABLE. II

Polarity of S3701 digits. 6 tov 0 6 7 s 9 0 Digit position A R A R A R A R A R o. D. o. l D. o. 9:. -/D; C D; C. 8-. DLC. r-it"s" f 6 D. w l ing r St0pl The operating requirements for a lever type rectifier sender are:

a. When the lever for a short positive pulse (any digit 1 to 5, seev Table I) is pulled to the finger stop, the direct current telephone circuit is cut out and the rectifier negatively polarized is introduced into the line circuit and remains in the circuit so polarized as long-as the finger lever 40 home position, in which position the rectifier is again cut; out andthc; direct, current telephone bridge introduced.

1). When the lever for, along positive pulse (any digit 6 to 0, see Table II). is pulled to the finger stop, the D. C. telephone circuit is cut out and the rectifier positively polarized is introduced into the line circuit and remains in the circuit so polarized as longas the finger lever is held against the finger stop and until it has been released and has passed to the second position when the polarity of the rectifier is reversed. The reversals continue as each position is passed beyond the second position until the home position is reached, in which position the rectifier is again out out and the direct current telephone bridge introduced.

GENERAL CIRCUIT OPERATION Thecircuits of Figs. 5,, ,6. and 7, when Fig, 6,, is placed below Fig. 5 and Fig. '7 below Fig. 6, show the register circuit connected to a calling subscriber line. When the subscriber calls, his line is connected to a register circuit through selector switches represented bythe box? H) in Fig. 5 in the well known manner, as described inmy prior patents. If the. subscribers, station is equipped, as shown in Fig. 5,.with a: dial for open circuit pulsing, the special classfipotential PC isnot .connectedto the register. If the'subscriberfs station isequipped with arectifier-sender (Figs. 8 and 9) for rectifier pulsing: the; class 15 pulses from the sub-station sender, and. a group of pulse counting and storing relays for each digit of a number tov berecorded. Onesuch group of pulse counting and storing, relays is shown. in Fig. 7'.

The pulse counting and storing.) relays hold the number and connect the proper selection potential PD corresponding; to the. stored digit to the selection control circuit of the register, which is not. shown, to establish a: desired connection. When the connection; is established, the calling line is connected to the called line by the link circuits indicated by the. box ll] of Fig. 5'if the lineisv free, or the callingpartyreceives the busy tone: if the line is unavailable.- and. the register. is released and. restored to normal. The manner in which these operationsare-performed isshown and described; in my prior patents and is; not shown in the drawings as they form no part of the present invention.

DETAILED OPERATION. OF CIRCUIT ON- OPEN CIRCUIT PULSING,

The pulse receiving circuit, Fig. 6' of. the register normally places negative direct current on the pulsing circuit so. that no change, in the pulsing circuit is required when a line equipped with an open circuit dial calls.

When the subscribers line is connected to the register, Fig. 6, PR! and PR2 operate in multiple, in a circuit from ground, windings. of PR! and PRZin parallel, back contacts of NBR inparallel, back DHR to battery. PRI and PR2 make'their front contacts and energize the register slow release relay DBR which does not fall off during dialling. The condensersyCl' and C2 are disconnected and the rectifiers SI and S2 short-circuited by NBR.

Subscriber dials the: dzgz'ttll The digit:0.is selectedto indicate how-the pulses for any digitiroml to.-0. are received. andrstored First pulse When the subscriber releases the finger wheel of the dial, the line circuit is momentarily opened. Prl and PR2 break their front contacts and make their back contacts. PRI energizes OCRI in a circuit from ground, back PR1, front DBR, back NBR, back OCR2, winding OCRI to battery. Slow releasing changeover relay DDR is energized over both its windings through front contacts of DBR and back contacts of PR2 and FBI.

The circuit of the right front contact of OCRI is normally open at front PCRI and PCR3 (pulse counting relays, Fig. 7) so that no pulse counting relay is energized on the first pulse and positive potential PDl remains connected to the register tube circuit (not shown) over back PCRI, 2, 3, 4 and 5 via conductor PD.

The reclosure of the line circuit by the dial terminates the first pulse and re-energizes PR! and PR2 which break their back contacts and make their front contacts. When PR1 breaks its back contact, it removes the short circuit over front OCRI from OCR2 so that OCR2 operates in series with OCRI with circuit through front OCRI, back OCR2, winding OCR2, front DDR to ground. OCR2 operates and locks up to ground in a circuitfrom ground, front DDR, winding OCR2, front OCR2, back ECR2, resistor R to battery. The left hand contacts of relay OCR2 are of the make-before-break type. OCR2 disconnects itself from OCRI which disconnects itself from the open back contact of OCR2 and releases.

During pulsing DBR does not fall off when PRI and PR2 break their front contacts, and similarly, DDR does not fall off when PRI and PR2 break their back contacts.

Second pulse When PRI makes its back contact at the beginning of the second pulse, it energizes ECRI over front OCR2. ECRI energizes pulse counting relay PCRI in a circuit from ground, front ECRI, back PCR6, back PCR2, winding PCRI to battery. PCRI locks up to ground via front PCRI, back PCR2, 3 and 4, resistor R9, back PCRG to ground. PCRI transfers the PD-potential applied to the register tube circuit from PDI to PD2.

At the end of the second pulse, the line circuit is reclosed for the second time and PRl breaks its back contact and makes its front contact. The short circuit is removed from ECRZ, which operates in series with ECRI and then locks up in a circuit from battery, resistor R, front ECRZ, winding ECR2, back OCR! and front DDR to ground. The right hand contacts of relay ECRZ are of the make-before-break type. The Operation of OCR2 releases ECRl' and OCR2. It will be noted that relays OCR! and OCR2 operated in sequence during the first pulse and relays ECRI and ECR2 operated in sequence during the second pulse. These relays continue to operate in the manner for succeeding pulses: OCR! and OCR2 for odd pulses and ECRI and ECR2 for even pulses.

Third pulse When the dial opens the line circuit for the third time, PRI energizes OCRI as on the first pulse. OCRI releases ECRZ and energizes PCRZ via front OCRI, back DCRZ, back PCR5, front PCRI, winding PCR2 to battery. PCRZ locks up to ground over the same circuit which looked PCRI, releases PCRI and places potential PD3 on the tube circuit.

Fourth and fifth pulses Sixth pulse The sixth pulse energizes even counting relay ECRI which energizes PCRB in a circuit from ground, front ECRI, back DCRZ, front PCR l,

back PCRE, Winding PCRS to battery. FORE GD- erates and opens the locking circuit of PCR4 which releases. PCRB locks itself to the front contact of ECRI over back PCRE.

At the end of the sixth pulse when PRI breaks its back contact, ECR2 again locks up and releases OCR2 and ECRI. When ECRI breaks its front contact, it removes short circuit from PCRS' which now looks up in series with PCR6 in a circuit from ground, front PCRG, winding 'PCR5, winding PCRS to battery. These two relays remain locked up during the remaining four pulses. Relays PCRI to PCR4 are all on their back contacts.

The X in the circuit between battery and the winding of relay PCRB and also in other circuits is intended to indicate that additional contacts not pertinent to the invention are included for releasing the relay.

When PCR5 makes its front contact, it places potential PDG over back PCRl, 2, 3 and 4 and front PCR5 on the tube circuit.

Seventh pulse PCR5 reverses the connection between the front contacts of OCRI and ECRI and the pulse counting relays PCRI to PCR4 so that when the seventh pulse is received and energizes OCRI, PCRI is energized in a circuit from ground, front OCRI, back DCRZ, front PCR5, back PCR2, winding PCRI, to battery. PCRI locks up to ground via front PCRI, back PCR2, 3 and 4, resistor R9, front PCR5 to ground and places potential PD'l on the tube circuit.

Eighth pulse The eighth pulse is received by ECRI which energizes PCRZ in a circuit from ground, front ECRI, back DCRZ, front PCRB, front PCR5, front PCRI, winding PCR2 to battery. PCRZ locks up to ground via front PCR5, releases PCRI and places potential PDS on the register tube circuit.

Ninth and tenth pulses The ninth and tenth pulses are received by OCRI and ECRI respectively, which energize PCR3 and PCR4 respectively. The former releases PCR2 and places PD9 on the tube circuit; the latter releases PCR3 and placed PDD on the tube circuit.

Table III is given for convenience in following the operation of the various relays involved in counting and storing pulses.

TABLE III For open circuit pulsing [f'ziront contact; b=back contact] .15 112552 52 Operating Circuit Digit counting relays operated When DDR is energized at the start of the pulses of a digit, DCRI is energized in a circuit from. ground, front EUR, back DCRZ, winding DCRI to battery. DCRI connects the winding of DCRZ to ground but DCR2 does not operate since it remains short-circuited in the well known manner over front DDR as long as DDR, remains energized.

When the pulsing of a digit is finished, the line circuit remains closed and holds FBI and PR2- operatecl long enough to release DDR. When DDR breaks its front contact, it releases the locked up odd and even counting relays and removes the short circuit from DCR2. DCR2 locks up in series with DCRI and transfers the four connections from the first group of counting and storing relays PCRI to PCRB, inclusive, to the next group of counting and storing relays, not shown. At the same time DCRZ places ground On conductor ST which energizes the selection oon trol circuit (not shown), to cause the first and subsequent selection to take place as rapidly as the digits are dialled.

Digit stored With DOB! and DCRZ energized, the pulsing circuit is ready to receive, count and store the next digit. The pulse counting relay or relays energized remain locked up until the register is released.

DETAILED OPERATION OF CIRCUIT WITH RECTIFIER PULSING A station equipped with a rectifier sender has the dial D replaced by the reversible rectifier S3 and the direct current bridge DB, as shown in Figs. 8 and When a station equipped with such a rectifier sender calls, the line relay places a special PC potential on the T-terminal of the subscriber's line in a manner not shown, which operates relay (3R2 in the register circuit of Fig. 6, to energize NBR and prepare the register circuit for receiving rectifier pulses. NBR does the following:

a. Locks up to ground over its front contact.

b. Shunts pulsing relays PR! and PR2 by condensers Cl and C2 respectively to prevent them from chattering on alternating current.

0. Removes short circuit from rectifiers SI and S2.

02. Disconnects the front contact'of PRI from the winding, of BBB and in place thereof connects it to the winding of DJR.

e. Disconnects the odd and even counting relays from. the back contact of PR! and connects back PRI directly to the pulse counting relays.

1. Places battery on the winding of. DHR,

g. Connects armature of DJR to back PRI.

When the subscribers station (Fig. 9) is connected to box Iii of Fig. 5, and thence to the pulse receiving relays (Fig. 6) PR! operates in series with the closed line circuit and rectifier SI. PR2 does not operate because S2 is so polarizedv as to prevent the passing of negative current.

PRi energizes slightly slow release relay DJR over front NBR and DJR energizes register slow release relay DBR.

As PR2 is not energized, a circuit is established when DBR closes its front contacts, from ground, back PR2, front DBR, one Winding of DDR, resistor R5 to battery. DDR, as previously stated, is slightly slow releasing and provides holding grounds during pulsing.

The circuit remains in this condition until the subscriber pulls the lever of the sender to the finger stop and, as previously described, rectifier S3, positively or negatively polarized according to the digit called, is introduced into the line circuit.

Subscriber dials the digit 5 The digit 5 is selected to indicate how the pulses for any digit from 1 to 5 are received and stored. Table I shows the order, polarity and number of pulses.

When the finger lever is started towards the finger stop, the direct current bridge DB is connected and remains connected until the finger stop is reached, whereupon the rectifier S3, negatively polarized, is introduced into the line circuit (Fig. 8), as previously explained and as shown in Table I, and since negative battery is already connected, PRI remains energized and no change takes place in the circuit as long as the finger lever is held against the finger stop.

When the finger lever is released, the polarity of rectifier S3 is immediately reversed and becomes positive (start of first pulse), as shown in Fig. 9 (also see Table I). PR1 releases and makes its back contact and in so doing energizes DHR in a circuit from ground, back PRI, front DBR, back DER, winding DHR, front NBR to battery. DHR operates and does the following:

a. Locks up to ground through resistor R1 and front DDR.

I). Disconnects the pulsing relays from battery and in place thereof, connects them to the alternating current source, indicated at A. 0., through resistor R2.

0. Connects the pulse. counting relays to back PR2. of the. make-before-break type.

When alternating current is connected to the line, PR2 operates on the pulsating positive pulse in series with rectifiers S2 and S3. PR2 breaks The right hand contacts of relay DHR are.

11 its back contact very rapidly as it is a very sensitive relay, so that PCRI is not prematurely energized and potential PDI remains connected to conductor PD.

At the end of this short positive pulse and at the beginning of a negative pulse (second), PRI breaks it back contact and PR2 makes its back contact, thus energizing pulse counting relay PCRI in a circuit from ground, back PR2, front DBR, front DHR, back DFR, back DCR2, back PCR6, back PCR2, winding PCRI to battery. PCRI locks up to ground through resistor R9 (see Table IV) and connects PD2 to conductor PD.

At the beginning of the third pulse, PRI makes its back contact and energizes PCR2 to connect PD3 to conductor PD. PR2 breaks its back contact.

At the beginning of the fourth pulse, PR2 makes its back contact and energizes PCR3 to connect PD4 to conductor PD. PRI makes its front contact.

At the beginning of the fifth and positive pulse, PR1 makes its back contact and energizes PCR4 .to place potential PD5 on conductor PD. PR2

makes its front contact but does not break it again as S3 is replaced by the bridge DB in the home position (see Table I) During the rapid opening and closure of the front contact of PR'-, DJR does not release.

Table IV is given for convenience in following the operation of the various relays involved in counting and storing pulses.

TABLE IV For rectifier pulsing 12 hold DBR. PR2 breaks its back contact with suiiicient rapidity to prevent a premature operation of PCRI.

As the rectifier S3, positively polarized, is introduced into the line circuit when the finger lever is within less than one position of the finger stop and remains in the line circuit as long as the finger holds the lever and until it has been released and returned one position (see Table II), the front contact of PR! remains open. This time interval is long enough to allowDJR to make its back contact which does two things:

a. It energizes DFR in a circuit from ground, back PRI, front NBR, back DJR, front DBR, back DFR, Winding DFR to battery. DFR locks up via front DDR and its own front contact.

6. After DFR makes its front contacts, a circult is established from ground, back PRI, front NBR, back DJR, front DBR, front DFR, back DCR2, winding PCR6 to battery. PCRB connects PCR5 but as long as PRI remains on its back contact it is short-circuited and therefore does not operate.

DFR reverses the connections between the back contacts of PRI and PR2 and the operating leads to the pulse counting relays but as PCR6 is energized, PCRI is not energized. The finger lever may be held indefinitely against the finger stop without change in the circuit condition. However, when the finger lever is released and moves into the second position (beginning of sec- Potential Digit counting relay DCR2 operated At the end of pulsing, the line circuit is again closed throu h the telephone circuit without rectifier S3. Thus both PR! and PR2 remain on their front contacts long enough to release DDR. When DDR breaks its front contacts, it removes short circuit from DCR2 which operates and transfers the leads from the pulsing relays to the next set of pulse counting relays and unlocks DHR.

Subscriber dials digit 0 This digit is selected to indicate how the pulses for any digit from 6 to 0 are received and stored (also see Tables II and IV).

When the finger lever is pulled toward the finger stop, the bridge DB remains until the beginning of the first position when rectifier S3, positively polarized, is introduced into the line circuit, as shown in Fig. 9, and as previously explained and as shown in Table II. Since negative direct current is connected to the line at this moment, both FBI and PR2, release and make their back contacts. PRI energizes DHR, as previously explained, which connects alternating current to the line, whereupon PR2 breaks its back contact and makes its front contact to 0nd pulse) on return and rectifier S3 becomes negatively polarized as indicated in Fig. 8 (also see Table II), PRI operates and breaks its back contact which removes short circuit from PCR5 which now locks up in series with PCRB and a circuit is established from ground, back PR2, front DBR, front DHR, front DFR, back DCR2, front PCR5, back PCR2, winding PCRI to battery. PCRI locks up in the usual way and connects PD! to conductor PD. When PR! makes its front contact, DJR is again energized and remains on its front contact during the remainder of pulsing.

When PRI makes its back contact for the second time, PCR2 is energized; when PR2 makes its back contact for the second time, PCR3 is energized; and when PRI makes its back contact for the third time, PCR I is energized and places PDO on the lead to the register, all as shown in Tables II and IV.

Digit counting relay DCR2 operated At the end of the fifth pulse, the line circuit is again closed and DDR releases as previously described, after which DCR2 operates. DDR releases DFR and DHR. DCR2 transfers the leads from the pulsing relays to the next set of pulse o nti g el y not shown.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention.

What is claimed is:

1. In automatic telephone system comprising a plurality of lines, a plurality of subscribers stations, sender means at a first of stations for sending direct current pulses of a single polarity over said lines corresponding to numerical digits, rectifier-sender means at a second of said stations for sending pulses of different polarities over said lines corresponding to numerical digits, register means adapted to be selectively coupled over said lines to either of said stations, said register means including separate means responsive to each type of pulse sent from said stations, said separate means comprising: a pair of pulsing relays, a pair of oppositely polarized unidirectional devices, each adapted to be serially connected to a different one of said pulsing relays, a first switch means operated when said second station is coupled to said register, additional relay means under control of said switch means, said additional means including a contact for controlling the connection of said uni-directional devices to said pulsing relays; a plurality of pulse counting relays connected in a chain and under control of said pulsing relays, said counting relays adapted to count the pulses received over said line from either of said stations, and to store said pulses for future transmission.

2. An automatic telephone system as claimed in claim 1, wherein said. register means further comprises a first source of uni-directional current, a second source of alternating current, a second switch means connectable between said sources and said uni-directional devices, said second switch means under control of said additional relay means and adapted to disconnect said first current source from said pulsing relays and to connect said second current source to said pulsing relays through said uni-directional devices upon operation of said additional relay means.

3. An automatic telephone system as claimed in claim 2, further comprising a line circuit interconnecting said second station and said register means, the rectifier of said sender means at said second station being connected to said line circuit when said sender is set to a sending position to indicate by its polarity which polarity of current from said second source is to be allowed to pass over said line.

GERALD DEAKIN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,886,216 Nilsson Nov. 1, 1932 2,272,464 Hensler Feb. 10, 1942 2,308,637 Babcock Jan. 19, 1943 2,406,001 Deakin Aug. 20, 1946 2,433,347 Deakin Dec. 30, 1947 

